Sierra Designs Flex Trail 40-60L Rucksack

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The spiritual little brother of the flex capacitor, the Flex Trail 40-60L Rucksack, can expand or contract depending on how much gear you take.

Sierra Designs says:

Flex on space, not on budget.

Explore like a pro no matter your experience level. The Flex Trail gives you the ability to tailor the pack size to your adventure needs by taking advantage of the horizontal gussets. Cinch it down to a 40L cargo capacity for your shorter trips. Expand it out to 60L for your longer adventures. Continue to customize your bag with the hardware-based adjustable torso. Keep your essentials close at hand with oversized mesh pockets and zippered hip pockets. The aluminum perimeter frame suspension keeps the pack weight light but the support strong

Our Verdict

The expandable volume of the Flex Trail is its unique selling feature. This bag has the ability to expand by 20L, which is game-changing in a 40L bag; your “night away bag” is now also your “week away bag.”

The U-shaped lid access to the pack body, a beautifully simple solution to the heavy lids featured on many similar packs. It makes for a rucksack that is refreshingly easy to pack and surprisingly spacious, even when fully cinched down. The Flex Trail veritably swallows gear while still providing dedicated space for a hydration bladder and keeping a small zipped essentials pocket in the roof, ideal for navigation kits and snacks.

The hip belt pockets are huge and can easily accommodate snacks, a phone, and a camera. The front mesh pocket is vast; these are now becoming standard with most rucksacks, especially in the American market. This large, accommodating pocket is perfect for storing wet weather gear, sit pads, and maps; having such items close at hand really improves the bag’s usability.

This a subjective point, but I also think the bag looks really good; the Flex Trail 40-60L Rucksack is the ideal solution to the age-old question of “what pack size do I need to take?”

– Reviewed by Ultralight Outdoor Gear

Features

• Expandable volume for versatility in use
• Lightweight aluminum perimeter frame
• Customizable fit with a hardware based adjustable torso
• Large front stretch mesh Shove-It pocket
• Zippered hip belt pockets and 2 stretch mesh side pockets
• U-shaped access to top zipper
• Zip stash pocket in lid

Specifications

• Weight: 1140g
• Volume: 39 – 56L (2380 – 3417 cubic in)
• Torso: 15.5” – 21” (39 – 53cm)
• Waist Belt: 31” – 54” (79 – 137cm)
• Dimensions (H x W x D): 27.5″ x 10.5″ x 14″ / 70 x 27 x 35 cm
• No. of Hip Belt Pockets: 2
• No. of Exterior Pockets: 5

Material & Construction

• 100D Nylon Honeycomb
• 420D Oxford

Help & advice:

• The Ultimate Guide to Choosing an Ultralight Rucksack
• Time-Saver Guide to Choosing a Rucksack